the die is cast, the irrevocable decision has been made; fate has taken charge:

The die is cast—I can't turn back.

Origin

1300-50;Middle Englishde (in early Modern English taking the vowel of the plural form dice) < Old Frenchde(i), presumbly < Latindatum given (neuter past participle of dare to give), perhaps in the derivative sense “put, placed,” hence “played, cast”

early 14c., des, dys, plural of dy (see die (n.)), altered 14c. to dyse, dyce, and 15c. to dice. "As in pence, the plural s retains its original breath sound, probably because these words were not felt as ordinary plurals, but as collective words" [OED]. Sometimes used as singular 1400-1700.

v.

"to cut into cubes," late 14c., from dice (n.). Meaning "to play at dice" is from early 15c. Related: Diced; dicing.

It has been speculated that Old English had *diegan, from the same source, but it is not in any of the surviving texts and the preferred words were steorfan (see starve), sweltan (see swelter), wesan dead, also forðgan and other euphemisms.

Languages usually don't borrow words from abroad for central life experiences, but "die" words are an exception, because they are often hidden or changed euphemistically out of superstitious dread. A Dutch euphemism translates as "to give the pipe to Maarten." Regularly spelled dege through 15c., and still pronounced "dee" by some in Lancashire and Scotland. Used figuratively (of sounds, etc.) from 1580s. Related: Died; dies.

die

n.

early 14c. (as a plural, late 14c. as a singular), from Old French de "die, dice," of uncertain origin. Common Romanic (cf. Spanish, Portuguese, Italian dado, Provençal dat, Catalan dau), perhaps from Latin datum "given," past participle of dare (see date (n.1)), which, in addition to "give," had a secondary sense of "to play" (as a chess piece); or else from "what is given" (by chance or Fortune). Sense of "stamping block or tool" first recorded 1690s.